Can someone give me a detailed explanation of the differences between 而 and 而且 /// 改变 and 变 ？

For some reason, these points will not sink in, I can't see the actual difference and it keeps screwing me on essays...

Anyone? Please? :D

(Sorry I won't be able to write Hanzi, too lazy to switch OSes or install iBus.)

AFAIK er2 can also function as "and", while er2qie3 is more likely to be used as "moreover" or "also". In my experience I've been taught to couple er2qie3 with bu4 dan1 earlier in the sentence, so it's "bu4 dan1 ... er2qie3". Example:

Budan ta shi yige pengyou, erqie shi yige hen shanliang de pengyou.

"Not only he is a friend, but also a good friend."

Gai3bian4 and bian4 only differs in that the gai3 in the first phrase is a verb, and the bian4 is a complement of result. Bian4 in itself is a verb. It's like saying bian4cheng2. Bian4hua4 however is a noun.

Someone please correct me if I'm wrong...